This ratio calculator does the three ratio jobs that come up most often. Solve a proportion by filling in three of the four boxes in A : B = C : D. Simplify a ratio of two or more parts, including decimals, so 1920:1080 becomes 16:9. And divide an amount in a ratio, such as sharing 1,000 in the ratio 2:3:5.
It is handy for recipes, scaling drawings and maps, mixing concrete or paint, splitting profits or bills, and school maths. Every result updates as you type and shows the working.
How to use the Ratio Calculator tool
- To solve a proportion, enter three values in A : B = C : D and leave one box empty.
- Read the missing value and the formula used to find it.
- To simplify, type a ratio with colons, for example
12:18:30. - To divide an amount, enter the total and the ratio to see each share.
Why use ToolOrca Ratio Calculator
- Solve A:B = C:D for any missing value
- Simplify ratios with two or more parts
- Works with decimals
- Shows 1 : n form and percentage shares
- Divide an amount in any ratio
- Live results with the working shown
How ratio calculations work
Proportion: A : B = C : D means A ÷ B = C ÷ D, so the missing value is found by cross-multiplying. If 3 : 4 = 15 : D, then D = 4 × 15 ÷ 3 = 20.
Simplify: divide every part by the greatest common divisor. 1920 : 1080 has a GCD of 120, giving 16 : 9.
Divide an amount: add the parts, then each share is total × part ÷ sum. 1,000 in 2 : 3 : 5 gives 200, 300 and 500.
Frequently asked questions
How do I simplify a ratio with decimals?
Type it as it is, for example 1.5:2.5. The calculator scales the parts to whole numbers and then simplifies, giving 3 : 5.
How do I find the missing number in a ratio?
Enter the three known numbers in the proportion boxes and leave the unknown one empty. The answer appears in the empty box.
How do I share money in a ratio?
Enter the total in Divide an amount in a ratio and type the ratio, for example 1:2. Each person's share is listed in the table.
What is the aspect ratio of 1920 × 1080?
16:9. For screens and images, our aspect ratio calculator also works out new widths and heights.